In classical microbiology, developing a high-efficiency bacterial consortium is a great challenge for faster biodegradation of petroleum contaminants. In this study, a systematic experimental and mathematical procedure was adopted to establish a bacterial consortium for the effective biodegradation of heavy oil constituents. A total of 27 bacterial consortia were established as per orthogonal experiments, using 8 petroleum-degrading bacterial strains. These bacteria were closer phylogenetic relatives of Brevundimonas sp. Tibet-IX23 (Y1), Bacillus firmus YHSA15, B. cereus MTCC 9817, B. aquimaris AT8 (Y2, Y6 and Y7), Pseudomonas alcaligenes NBRC (Y3), Microbacterium oxydans CV8.4 (Y4), Rhodococcus erythropolis SBUG 2052 (Y5), and Planococcus sp. Tibet-IX21 (Y8), and were used in different combinations. Partial correlation analysis and a general linear model hereafter were applied to investigate interspecific relationships among different strains and consortia. The Y1 bacterial species showed a remarkable synergy, whereas Y3, Y4, and Y6 displayed a strong antagonism in all consortia. Inoculation ratios of different strains significantly influenced biodegradation. An optimal consortium was constructed with Y1, Y2, Y5, Y7, and Y8, which revealed maximum degradation of 11.238 mg/mL OD₆₀₀ for oil contaminants. This study provides a line of evidence that a functional consortium can be established by mathematical models for improved bioremediation of petroleum-contaminated environment.

The rheology of a partially hydrolyzed polyacrylamide (HPAM) solution plays an important role in its oil recovery during polymer flooding. However, multiple factors in brine, such as sulfide ions, cause a dramatic loss in the viscosity and oil recovery. To better understand the sulfide-induced viscosity loss and the consequent flow mechanisms in pore networks, the morphology of polymer solutions with and without sulfide ion was observed by scanning electron microscopy; and the variations of the pore scale flow fields were demonstrated by a microscopic visualization seepage experiment combined with Micro-PIV (Microscale Particle Image Velocimetry). The results showed that, with the presence of sulfide ion, the microstructure of the polymer changed from a uniform three-dimensional network structure to loose and uneven floccules, which resulted in viscosity loss (over 70% with 5-mg/L sulfide ion). Moreover, higher concentrations of sulfide ions (5 mg/L and 10 mg/L) resulted in earlier shear thinning characteristics than those with lower sulfide concentrations. Due to viscosity loss, the average flow velocity in the main stream of the microscopic seepage experiment increased more significantly than that without sulfide. However, the viscosity loss alone cannot independently explain the severe viscous fingering during the subsequent post-water flooding, which was about five times greater than that of the primary water flooding in terms of the velocity ratio between the mainstream and margin. A further pore-scale flow field analysis exhibited an eccentric and a bimodal velocity distribution in the throat along the radial and axial directions, respectively. The former distribution indicated that the adsorbed polymer on the pore wall was broken through by hydraulic shear due to the collapsed structure caused by sulfide ion. The latter suggested that another sulfide-induced impact was an earlier-occurring non-Newtonian characteristic with a low shear rate. Therefore, instead of viscosity loss, elastic loss is the dominant mechanism affecting the characteristics of the aggregate flow field under the action of sulfide. Microscopic flooding combined with Micro-PIV is a feasible and essential method to reveal pore scale flow mechanisms.

Purified terephthalic acid (PTA) is an extremely important bulk organic raw material; it plays a central connecting role in the PX–PTA–polyester industry chain, while its significant carbon intensity remains poorly quantified. Through process-level life cycle assessment (LCA) based on in situ industrial data, this study establishes a comprehensive material-energy inventory for PTA production. The results show that the total greenhouse gas (GHG) emissions of the entire PTA process reached 1600.9 kg of CO₂ eq·t⁻¹, exceeding those of common primary chemicals, like aromatics, butadiene and styrene. The end process of the PTA unit (PU) dominates GHG emissions, reaching 365.6 kg CO₂ eq·t⁻¹, accounting for 22.3%, driven by extra xylene input, various catalyst consumption, auxiliary chemicals, and energy intensity. After allocating steam-related emissions from coal-fired power stations, the GHG emissions of the PU rise to 400.9 kg CO₂ eq·t⁻¹. Sensitivity analysis demonstrates that replacing conventional hydrogen with green hydrogen slashes hydrogen-related global warming potential (GWP) contribution by 61.5%. In addition, a 10% increase in electricity, coal, or steam elevates system GWP by 0.80%, 0.036% and 2.48%, respectively. The findings demonstrate that energy structure optimization and green hydrogen integration represent decisive levers for PTA decarbonization, providing data-driven insights for industrial transition under a carbon reduction policy framework.

Purified terephthalic acid (PTA) is a key intermediate in the global polyester industrial chain, and its carbon intensity directly governs the sustainability of downstream products. The production of PTA involves high-temperature oxidation and catalytic refining processes, generating large volumes of organic wastewater whose on-site anaerobic treatment converts dissolved organic carbon into methane. This study presents a gate-to-gate process emission assessment methodology for PTA production, coupling energy-based emission factors, process carbon balance, and wastewater methane accounting within the system boundary, thereby extending conventional process-accounting frameworks. Based on a gate-to-gate life-cycle assessment of four representative PTA production systems across three industrial settings, we quantified emissions from energy consumption, process-related carbon losses, and wastewater treatment, with particular emphasis on the methane generated in the anaerobic treatment stage. Results demonstrate that steam constitutes the dominant carbon-emission contributor, accounting for 62–70% of total emissions, indicating that heat structure and recovery optimization are the highest-priority targets for emission reduction. According to carbon-flow analysis, although PX accounts for 97–98% of total carbon input, PTA products retain 95–97% of the carbon. Critically, wastewater treatment emerges as a significant yet overlooked emission pathway of methane generated during anaerobic digestion owing to its high global warming potential (GWP), so omitting methane emissions from wastewater treatment understates the total emission intensity by 7.5% to 10.8%, whereas the wastewater-treatment stage as a whole contributes 10.84% to 16.13% of total emissions. In addition, the results provide local carbon-emission factors for similar technologies, with advanced technology systems achieving 0.214 t CO₂/t PTA, while less integrated systems reach 0.395 t CO₂/t PTA. Low-carbon steam supply, improved heat integration, oxidation-loop control, solvent-cycle stability, and methane capture or oxidation in wastewater treatment are therefore important measures for reducing emissions, supporting the Sustainable Development Goals of responsible consumption and production and climate action. This integrated approach provides actionable insights for guiding low-carbon process optimization and more accurate carbon-accounting practices in the PTA industry.